This invent generally relates to electrooptical devices.
Photons, like electrons, can carry information from one place to another. Photons, however, have some distinct advantages over electrons which make them a particularly attractive transmission media. For example, photons generally do not interact with each other as do electrons. Consequently, different light beams can pass through one another or share the same optical fiber without resulting in crosstalk between the beams. In addition, the electromagnetic spectrum associated with photons covers much higher frequencies than the electromagnetic spectrum associated with electronic communication. Thus, the information-carrying capability of a light beam is correspondingly higher than that of an electronic signal. Furthermore, light beams need not be confined to an optical fiber or a waveguide whereas electrons must be confined to a wire or other conductive path. As a result, light beams can simultaneously communicate information to many members within an array of receivers without requiring a complex network of interconnections. And, of course, light signals can move through a circuit at a rate limited only by its velocity of propagation and not limited by RC (i.e. resistance-capacitance) charging times.
Attempts to construct circuits which process light signals rather than electrical signals have met with significant obstacles, however. A major problem has been the scarcity of optical devices which are analogous to the different electrical devices used in electronic circuits. For example, there has been no satisfactory optical device comparable to a flip-flop, the fundamental building block of most digital computers. Indeed, because photons do not interact with each other, it has been difficult to design such a device, or, for that matter, any device in which one light beam modulates another light beam.